Electron discharge device



March 8, 1949. w, c, w I 2,463,512

ELECTRON DI SCHARGE DEVICE Filed June 1, 1945 2 Sheets-Sheet 1 MODULATION SIGNA EGZ/ AWm/rom fV/zu/w 0. 15mm;

March 8, 1949. w. c. BROWN ELECTRON DISCHARGE DEVICE Filed June 1, 1945 2 Sheets-Sheet 2 Illll Patented Mar. 8,

iiiti'itili didiiid i tiiilhl'l @FMCE- ELECTRON DKSCHARGE DEVICE VYiliiarn C. hrown liineoln, Mass, assignor to Ptaytheon Manufacturing Company, Newton, Mass, a corporation of Delaware p'plication a a...

8 Claims. l

My present invention relates to electron-discharge devices, and more particularl to tuning means therefor.

My present invention is especially suitable for tuning or frequency modulating electron-discharge devices adapted to generate electrical oscillations having a wave length of the order of a few centimeters or less, for example, devices of the so-called magnetron type.

One of the objects of my present invention is to provide tuning means for an electron-discharge device of the general character indicated which enables the attainment of increased frequency deviation.

Another object of my present invention is to accomplish the foregoing in a simple andinexpensive manner.

These, and other objects of my present invention, which will become more apparent as the detailed description thereof progresses, are attained, briefly, in the following manner:

I prefer that my present invention be applied to an electron-discharge devic comprising, in general, a centrally-disposed cathode structure, an anode structure spaced from and surrounding said cathode structure, and incorporating a plurality of radial cavity resonators, means for establishing a magnetic field in a direction perpendicular to the electron-path between said cathode and anode structures, and a pair of conducting straps electrically connected to points of opposite polarity on each of said cavity resonators.

When a proper voltage is applied between the cathode and anode structures of such a device, and the magnetic field thereof is properly adjusted with respect to the electric field created by said voltage, such a device generates electrical oscillations of a wave length determined by the inductance and capacitance incorporated therein as a function, primarily, of the geometry of the physical elements making up the aforementioned cavity resonators.

Now it has been found that by introducing a stream of electrons into one or more of the cavity resonators of such a device, and altering the space charge. created by said electrons, the resonant frequency of the device can be changed. Hence, appropriate alteration of said space charge results in frequency modulation of the device.

For this purpose, and in accordance with my present invention, I so dispose an electron-source and an electron-collecting anode with respect to the above mentioned cavity resonators that a pluralit of electron-paths through high-capacie 1, 1945, Serial No. 597,069

tance regions of said cavity resonators are presented between said electron-source and said col-- lecting anode. Then, by adjusting a magnetic field, which passes through he space charge regions thus created, in a direction transversely of said e1ectron-paths, so that the orbital frequency of the electrons differs slightly from the natural resonant frequency of the device, I am able to obtain maximum tuning efiect; and by suitably modulating the density of said space charge, preferably, by utilizing the cavity resonators themselves as control electrodes, I obtain corresponding modulation of the frequency of the device. 1

In the accompanying specification I shall describe, and in the annexed drawings show, andlustrative embodiment of the electron-discharge device of my present invention. It is, however,

to be clearly understood that I do not wish to be limited to the details herein shown and described ior purposes of illustration only-inasmuch as changes therein may be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

- In said drawings:

Fig. 1 is a fragmentary, longitudinal sectional view of an electron-discharge device of the socalled magnetron type incorporating electronic tuning means made in accordance with theprinciples of my present invention;

Fig. 2 is a transverse sectional view of the same taken along line 22 of Fig. 1; and

Fig. 3 is a fragmentary, enlarged longitudinal sectional View more clearly showing the .relationship between the above-mentioned electronsource, collecting electrode, and cavity resonators.

Referring now more in detail to the aforesaid illustrative embodiment of my present invention, and with particular reference to the drawings illustrating the same, the numeral 5 generally designates an electron-discharge device of the socalled magnetron type.

As herein shown, said device includes an anode structure 6, a cathode structure l, magnetic means 8 for establishing a magnetic field in a direction perpendicular to the electron-path between said cathode and anode structures, and tuning means 9.

The anode structure 6 preferably comprisesa cylindrical body It, made of highly conductive material, such as copper, and provided With'a plurality of anode members in the form of the interiorly-extending, radially disposed vanes H.

The cylindrical body H] is closed at its endsby plates I2 and I3, the junctions between said body and said plates being hermetically sealed, as at I4.

The cylindrical body In is of such diameter, and the number, size and relative spacing of the vanes II are so chosen that each pair of adjacent vanes, together with that portion of said cylindrical body lying therebetween, define a cavity resonator at the unaltered frequency desired of the output of the device.

The cathode structure 1, which is coaxial with the anode structure 6, preferably comprises an elongated sleeve I5, conventionally made of nickel or the like, and having a reduced portion I 6 which is substantially coextensive with the vertical dimension of the vanes I I, in other words, with the length of the cavity resonators, and provided with a highly electron-emissive coating IT, for example, of the well-known alkaline-earth metal oxide type.

In order to support the cathode sleeve I with respect to the anode members I I, said sleeve may be reduced at its lower end I8 to fit into a tubular conducting member I9, the latter, in turn, being insulatedly supported, in any desired manner, not shown, by a tubular pole piece 20 hermetically sealed, as at 2I, into the end plate I2, said pole piece being provided with a bore 22 through which the cathode structure may enter the device.

The cathode sleeve I5 may be heated by a filament 23 connected at one end 24 to said sleeve, and at the other end 25 to a lead-in conductor 26 suitably entering the device through the tubular conducting member I9. Current may be conveyed tothe filament 23 by connecting the member I9, through a conductor 21, to the negative terminal of an appropriate source of voltage 28, and connecting the lead-in conductor 26, through a conductor 29, to a positive tap on said voltage source. The positive terminal of said voltage source may be grounded, as shown, as may be the cylindrical body I0, whereby a potential difference is established between the cathode structure I and the anode structure 6.

Another pole piece 30 is hermetically sealed, as at 3|, into the end plate I3, said pole piece, and the pole piece 20, being fixed, for example, at the opposite ends of a horseshoe magnet, not shown, the two pole pieces and the horseshoe magnet constituting the above referred to magnetic means 8 for establishing a magnetic field transversely of the electron-path between the cathode and anode structures of the device.

I provide the vanes I I, preferably, in the lower edges thereof, adjacent their inner ends, with slots 32 receptive of a pair of concentric, conducting straps 33 and 34, said straps alternately contacting successive vanes I I. It has been found that when alternate vanes are electrically interconnected, as by the straps just described, the tendency of the device to generate spurious oscillations, which would reduce its efliciency, is eliminated.

In the device as thus far described, there is no means for controlling the frequency thereof, and in order to provide such means, I prefer to proceed as follows:

I provide each of the vanes II, preferably, at the upper edge thereof, near its inner end, with an extending wing 35, the space 36, see Fig. 2, between the wings of each pair of adjacent vanes constituting a high-capacitance region of the corresponding cavityresonator and, as will be shortly described, presenting an electron-path which lies transversely of the electric-field component of radio-frequency oscillations generated in said corresponding cavity resonator, and also, of the magnetic field, more particularly, the leakage field between the pole pieces 20 and 3!].

I surround the Wings 35 with a hollow, annular cathode member 37 provided, on its exterior surface, facing the wings 35, with a highly electronemissive coating 38. Said cathode member may be heated by means of a filament 39 enclosed within the same and connected, at diametrically opposed points 46 and 4|, to lead-in conductors 42 and 43 which, in turn, may be connected across the secondary winding of a filament transformer 44. The primary of said transformer may be connected to a suitable source, not shown, of filament voltage.

The lead-in conductor 42 may enter the cathode member 31 through a conducting bushing 45 which is fastened to said cathode member, and the lead-in conductor 43 may enter said cathode member through an insulating bushing 46 which is, likewise, fastened to said cathode member.

The lead-in conductors 42 and 43 may enter the device, itself, respectively, through glass seals 41 and 48 fused into the outer ends of pipes 49 and 50 which are threadedly engaged and hermetically sealed into the end plate I3.

In order to cause the electrons emitted by the cathode member 3] to pass through the spaces 36 between the wings 35, I connect the lead-in conductor 42, through a conductor 5 I, to the negative terminal of a suitable source of voltage 52, the positive terminal of the latter being connected, through a current-limiting resistor 53, to a leadin conductor 54 which enters the device through the seal 41 and pipe 49, and is connected to an annular collecting electrode 55 supported, in spaced relation to the cathode 31, adjacent the inner edges of the wings 35.

It will be noted that the electron-paths 36 between the cathode 31 and the anode 55 are within the magnetic field, more particularly, the leakage field, between the pole pieces 20 and 30. It will also be noted that said electron-paths are within the radio-frequency field between the wings 35 which are integral with the cavity resonators. Hence, by adjusting the intensity of said magnetic field so that the orbital frequency of the electrons emitted by the cathode 31 is slightly different, either lower or higher, than the frequency of said radio-frequency field, a space charge of appreciable density is built up within the spaces 36 between the cathode 3! and the anode 55. I believe that the introduction of this space charge alters the dielectric constant of the high-capacitance regions intermediate the cathode 31 and the anode 55, and this, in turn, alters said capacitance, resulting in a change in the resonant frequency of the device.

I now provide means for altering or modulating said space charge, whereby the device as a whole may be frequency modulated. For this purpose, the cathode 31 is connected to the positive terminal of a suitable source 56 of bias voltage, the negative terminal of said voltage source being returned, through the secondary winding of a modulation transformer 51, to the body of the device itself, as at 58. The primary winding of the transformer 51 is connected across any appropriate source of modulating signals, Thus, the cavity resonators, or, more specifically, the wings 35 thereof, function as electrodes to control the flow of electrons between the cathode 31 and the anode 55, thereby tuning or modulating the device, as above explained, in accordance with changes in space charge density.

Inasmuch as it is preferable to keep alternating current out of the voltage source 55, the latter may be by-passed by a capacitor 59.

In order to extract power from the device, I provide a loop 6!} which may be introduced into any one of the cavity resonators defined by the anode structure 6, said loop entering said device through a glass seal (not shown) fused into a pipe 6| threaded and hermetically sealed into the cylindrical body I9.

This completes the description of the aforesaid illustrative embodiment of my present invention. It will be noted from all of the foregoing that I have provided a simple and inexpensive electronic tuning means for an electron-discharge device of the so-called magnetron type, said tuning means being disposed in a high capacitance region of the cavity resonators of such discharge devices, and enabling greater frequency deviation than it has heretofore been poshible to attain. It will further be noted that I have provided a simple method of utilizing the body of the device itself as a control electrode for obtaining the desired space charge modulation. Other advantages of my present invention will readily occur to those skilled in the art to which the same relates.

What is claimed is:

1. An electron-discharge device comprising: a cathode; an anode structure spaced from said cathode, and incorporating a plurality of cavity resonators in which radio frcqnency oscillations are adapted to be generated; means adjacent said cavity resonators for establishing a magnetic field through each; and means, cooperable with the electric-field component of said radio-frequency oscillations, and with said magnetic field, for set ting up a space charge in each such cavity resonator; said last-named means including an electron-source and a collecting electrode spaced therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonators and having a plurality of electronpaths therebetween which lie, respectively, within said cavity resonators, each, mutually perpendicuiar to said electric-field component and said magnetic field.

2. An electron-discharge device comprising: a cathode; an anode structure spaced from said cathode, and provided with a plurality of anode members; each pair of adjacent anode members, together with that portion of said anode structure lying therebetween, defining a cavity resonator in Which radio-frequency oscillations are adapted to be generated; means adjacent said cavity resonators for establishing a magnetic field through each; and means, cooperable with the electric-field component of said radio-frequency oscillations, and with said magnetic field, for setting up a space charge in each such cavity resonator; said last-named means including an electron-source and a collecting electrode spaced therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonators and having a plurality of electronpaths therebetween which lie, respectively, within said cavity resonators, each, mutually perpendicular to said eiectric-field component and said magnetic field.

3. An electron-discharge device comprising: a cathode; an anode structure spaced from and surrounding said cathode, and provided with a plurality of radially disposed, interiorly extending vanes; each pair of adjacent vanes, together with that portion of said anode structure lying therebetween, defining a cavity resonator in which radio-frequency oscillations are adapted to be generated; means adjacent said cavity resonators for establishing a magnetic field through each; and means, cooperable with the electricfield component of said radio-frequency oscillations, and with said magnetic field, for setting up a space charge in each such cavity resonator; said last-named means including spaced concentric cathode and anode members disposed adjacent said vanes and having a plurality of electron-paths therebetween which lie, respectively, Within said cavity resonators, each, mutually perpendicular to said electric-fieid component and said magnetic field.

4. A tunable electron-discharge device comprising: a cathode; an anode structure spaced from said cathode, and incorporating a plurality of cavity resonators in which radio-frequency oscillations are adapted to be generated; means adjacent said cavity resonators for establishing a magnetic field through each; means, cooperable with the electric-field component of said radiofrequency oscillations, and with said magnetic field, for setting up a space charge in each such cavity resonator said last-named means including an electron-source and a collecting electrode spaced therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonators and having a plurality of electron paths therebetween which lie, respectively, Within said cavity resonators, each, mutually perpendicular to said electric-field component and said magnetic field; and means, including each such cavity resonator as a part thereof, cooperable with said last-named means for varying said space charge.

5. A tunable electron-discharge device comprising: a cathode; an anode structure spaced from said cathode, and provided with a plurality of anode members; each pair of adjacent anode members, together with that portion of said anode structure lying therebetween, defining a cavity resonator in which radio-frequency oscillations are adapted to be generated; means adjacent said cavity resonators for establishing a magnetic field through each; means, cooperable with the electric-field component of said radiofrequency oscillations, and with said magnetic field, for setting up a space charge in each such cavity resonator; said last-named means including an electron-source and a collecting electrode spaced therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonators and having a plurality of elec tron-paths therebetween which lie, respectively, within said cavity resonators, each, mutually perpendicular to said electric-field component and said magnetic field; and means, including each such cavity resonator as a part thereof, cooperable with said last-named means for varying said space charge.

6. A tunable electron-discharge device comprising: a cathode; an anode structure spaced from and surrounding said cathode, and provided with a plurality of radially disposed, interiorly extending vanes; each pair of adjacent vanes, together with that portion of said anode structure lying therebetween, defining at least one cavity resonator in which radio-frequency oscillations are adapted to be generated; means adjacent each such cavity resonator for establishing a magnetic field therethrough; means, cooperable with the electric-field component of said radiofrequency oscillations, and with said magnetic field, for setting up a space charge in each such cavity resonator; said last-named means including spaced concentric cathode and anode members disposed adjacent said vanes and having a plurality of electron-paths therebetween which lie, respectively, within said cavity resonators, each, mutually perpendicular to said electric-field component and said magnetic field; and means, including each such cavity resonator as a part thereof, cooperable with said last-named means tron-source and a collecting electrode spaced M therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonator and having an electron-path therebetween which lies within said cavity resonator mutually perpendicular to said electric-field component and said magnetic field.

8. An electron-discharge device comprising: a

cathode; an anode structure spaced from said cathode, and incorporating a cavity resonator in which radio-frequency oscillations are adapted to be generated; means adjacent said cavity resonator for establishing a magnetic field therethrough; means, cooperable with the electric-field component of said radio-frequency oscillations, and with said magnetic field, for setting up a space charge in said cavity resonator; said last-.

named means including an electron-source and a collecting electrode spaced therefrom; said electron-source and said collecting electrode being disposed adjacent said cavity resonator and having an electron-path therebetween which lies within said cavity resonator mutually perpendicular to said electric-field component and said magnetic field; and means, including said cavity resonator as a part thereof, cooperable with said last-named means for varying said space charge.

WILLIAM C. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,163,157 Samuel June 20, 1939 2,409,038 Hansell Oct. 8, 1946 2,413,385 Schmidt Dec. 31, 1946 

